reserve E,X,Y,x for set;
reserve A,B,C for Subset of E;
reserve x1,x2,x3,x4,x5,x6,x7,x8,x9,x10 for Element of X;

theorem Th46:
 for X being trivial non empty set
  ex x being Element of X st X = {x}
proof let X be trivial non empty set;
  consider x being object such that
A1:  X = {x} by ZFMISC_1:131;
  reconsider x as set by TARSKI:1;
  x in X by A1,TARSKI:def 1;
  then reconsider x as Element of X by Def1;
 take x;
 thus X = {x} by A1;
end;
